Snap action device



Oct. 21, 1952 J. SCHMIDINGER 2,615,106

SNAP ACTION DEVICE Filed July 21, 1951 s Sheets-Sheet 1 BY 5 4 791 x 6 40140104 A '1 701m Y5 Oct. 21, 1952 SNAP ACTION DEVICE Filed July 21, 1951' If Sheets-Sheet 2 /Z a T1 .12.

INVEN TOR. (/OSFPA .stv/M/pwqm Q, Ma Afi o A TORNE VS .1. SCHMIUINGER 2,615,106

Oct. 21, 1952 J SCHMIDWGER 2,615,106

SNAP ACTION DEVICE Filed July 21, 1951 s Sheats-Sheet :5

TIET15. /!4

1:1.lE. 34 74 7536a 38 52 I N V EN TOR. (/OSE'PH SCHM/0/A/46k A TTORNE Y5 Patented Oct. 21 1952 UNITED STATES PATENT OFFICE SNAP ACTION DEVICE Joseph Schmidinger, Lake George, N. Y. Application July: 21-, 1951, Serial No. 237,958

I o1. 2o 0 ,113

'24,. C aims- 1 This invention comprises an efficient and simple snap action-device of wideapplication.

The device maybe employed for-thecontrol of electric circuits, for example as arelay as a flasher, or as'a circuit breaker, or it may beemployed as a temperature responsive device. It maybe actuated'by electrical forces, by thermal forces, or by mechanicalforces orbya combination thereof. The new device, irrespective of its particular application and of the particular ac tuating forces, comprises essentially three elements, namely, a disc, a laterally flexiblepull wire orstrip secured at its ends to the disc at opposite'ends of a diameter, and a support see cured to the flexible strip 'and'positioned. onthe geometrical axis of the disc but not fastened to the disc. The disc isof springmaterial and has a crease or bend formed therein along thev diameter thereof underlying the flexible strip, the

strip extending along the convex side of the crease in the disc. The flexible pull strip may be continuous between the points of attachment to the disc, in which case it is secured to the support. means at its midsection or the strip may be in two parts, in which caseone end of each section is secured to the support. 'In either case the pull strip is so mounted on the support as to be under longitudinal tension and the support is so constructed as to permit of adjustment or of variation of the, tension in the strip.

The disc under predetermined increase of tension in the pull strip, snaps from one position, that. in whi h. thehalves .of the .discon each side of thediametrica crease. extend outwardly away from the support at an included angleofless than .8.0. to a second pos tion. .Qnein which the disc. i bowed in he Qp osit dire tion about a d amete 9 t therr to med cr as in the entire periphe o the d s s fre t mQve.--,b, ns

unat ached o ny i id art. a a h s 51. 2 m 9f e de iq t e cent a y oca ed supr means 9 whi h he pu strip s secu d. un rm and re ime sna tt e Q the i es hi w ll b sr la nesi in ore detai hereinafter.

W t e dev ce i t qp raiei alie gr. 195? electrical contacts andis itself to carry current,

he sis? and stri a e i were are electrica Contact w e tq hweeier at the dis on he o both" ide fih req i e nd ns upon I the circuitor circuits to be controlledand the location of cooperating fixfid contacts. Th iiexb nul steele h' a p i e q e hr s a ans l nu l w re whiv 1w eii heat b a s g e-t de ram 19? i iree af el mits the disc to assume the form to which it is constrained by the diametrical crease thereinbut which when cold or when carrying a limited amount of current,causes the'disc to snap and buckle in the opposite direction.

When the disc and pull strip are of material having the same coefiicient of thermal expansion, its operation is not affected by the ambienttemperature as both disc and pull strip will expand and contract together and this is a decided advantage for many applications of the device. When, however, response to ambient temperature is desired, as when the device is tobe employed as ,a thermostat, the disc and pull strip" are made of materials having different coeff cients of thermal expansion, in which case proper e t o o the es ct ve m rials n b the initial tension in the flei ible pull strip, pQsitive snap. man o th d e r pe e o ambient temper e ma b Oht eqi I As heretofore indicated,the sole support means for-the device is centrally'located andengages the pull strip only. Ifhe support each ca se includes means for adjusting the initial tension in ihewll, S r p- Thi is th 'us ns man required or wanted for the device." 'rmsreatur is important as it avoids any stressing of the disc which inherently results when forces are applied directly to the disc during attachment 10f the strip or after such'attach'ment. When the device is to be ,rn echanically rather than thermally actuated, the tension in the pull strip is controlled by the support means which, in this case, is constructed to include such tension varying means as well as the means for initially adjusting the'devicef For, a better understanding of the new snap action device and of various fields of application t s t en thereof, reference may be had to ing drawings, of which: 1 is a top perspective view of one embodiment of the invention; I

Fig. 2 is a bottom perspective view of the structure shown in if Fig. 3 is a cross-sectional view along the line 3 3 of Fig. 4 is a top perspective view of the structure shown in Fig. 1 wit the center of the disc buckled upwardly; x Fig. 5 is a bottom perspective view of the structure shown in Fig. 4 m

Fig. 6 is a cross-sectional view takenalong the line 6-6 of Fig. 4}

Figs. 7 to lqarediagrammatic viewsexplanatory of the act on of the device and illustrating 3 th optimum location of a cooperating contact or other element to be actuated by snap action of the device;

Fig. 11 is a diagram illustrating the snap action device of Figs. 1 to 6 connected for control of a lamp load circuit;

Fig. 12 is a top view of a switch structure embodying the invention;

Fig. 13 is a cross-sectional view taken along the line l3-l3 of Fig. 12; I

Figs. i i-A and i i-B are fragmentary views or the disc supporting means of the structure of Fig. 12 showing the method of adjustment thereof;

Fig. 15 is a top view of a switch structure similar to that of Figs. 12 and 13 but provided with two adjustable fixed contacts, one for engagement by a disc carried contact in one position of the disc and one for engagement by a disc carried contact in the other position of the disc;

Fig. 16 is a cross-sectional view taken on the line Iii-45 of Fi 15;

Fig. 17 is a diagrammatic view illustrating one application of the structure of Figs. 15 and 16;

Fig. 16 is a sectional View of the snap action device of the invention arranged for actuation of switch contacts in response to mechanical variation of tension in the pull strip;

Fig. 19 is a horizontal sectional view taken on the line iii-i8 of Fig. 18; and

Figs. 20 and 21 illustrate other designs of constrained discs suitable for use in the snap action device of the invention.

Figs. 1 to 3 inclusive show a snap action d..- vice of the invention in the position correspon ing to reduced tension in the pull strip. The disc of the device is indicated at it, the flexible pull strip at i2 and the centrally disposed support generally at it. The disc is of spring material, for example metal, and has a diametral crease it therein which is parallel to and convex toward the pull strip ii. The crease is preferably formed by bending the disc through its center line over a round edge having a small radius of curvature, the disc being preferably subsequently heat trea ed to permanize the constraint therein. The crease should be relatively shallow so that the dihedral angle formed at the crease lies between 135 and 180, say 170. The flexible pull strip i2 is secured at its ends to the periphery of the disc ill adjacent the ends of the crease ill. The central section of the strip is secured to the support H3. The support H. comprises a having an externally threaded end axially slotted to provide furcations Ma and i i?) which, by means of a nut i'l threaded on the support, "may forced toward each other to reduce the width of the axial slot. The strip i2 is attached, as by welding or riveting, to the furcations 55c Nb and these points of attachment to the i'urcations are equidistant from the points of attachment of the strip to the disc and preferably eilected while the furcations are most widely separated. After attachment of the strip ii the nut i '5 is turned to introduce the desired tension in the parts of the strip radiating from support, thus introducing slack in the strip i2 intermediate the furcations, as indicated in Figs. 3 and 6. This arrangement provides a simple and effective means for adjusting the tension in the pull strip When the nut ii is rotated in a direction to move it closer to disc it, it draws the furcations i 50. and 14b closer and thereby increases the tension in the pull strip. When the nut is turned in the reverse direction the furcations or jaws move apart and reduce the tension in the pull strip.

Figs. 4-. to 6 illustrate the device of Figs. 1 to 3 when in the position corresponding to increased tension in the pull strip. In this position the disc is buckled along a diameter indicated by the line X-X in Figs. 4 and 5, at from the crease l5 and the center of the disc is displaced axially from the support.

The action of the disc in snapping from one position to the other under the influence of the tension exerted through the pull strip can be better illustrated by reference to Figs. 7 through 10, wherein the movement of the disc is shown exaggerated to facilitate explanation and understanding. Figs. 7 to 10 also illustrate the optimum positioning of a cooperating fixed element to be actuated by the snap action device. For convenience the support means are not shown in Figs. 7 to 10, nor that part of the strip 12 which is not under tension, namely, the section between the points of attachment to the furcations of the support. An important aspect of this snap action device is that the disc iii when forced to snap under tension of the pull strip, actually reverses its natural curvature with the greatest portion of such reversal occurring at the center of the disc. This results in the translation of practically all of the motive power of the pull strip into positive action at the center of the disc.

Another important aspect of the invention is that of a locking effect of the device in both positions of the disc. This results from a displacement of the disc through a so-called equilibrium position so that, as a disc snaps rapidly from the position shown in Fig. 1 to that shown in Fig. 4, the free edges of the disc swing downwardly while the center of the disc moves upwardly and at the same time the points on the periphery of the disc to which the pull strip is attached shift very little in comparison to either the free edges of the disc or the center thereof.

Fig. '7 is a substantial equivalent of Fig. 6, having the pull strip l2 in tension and the disc in snapped to its upward position. This position of the disc may be considered the normal at-rest position of the assembled device with the pull strip (2 in tension, assuming no cooperating fixed element to be actuated as, for example, a fixed contact to be engaged by a contact secured at the center of the disc.

Fig. 8 shows the position of the pull strip 12 and disc [0 in dotted lines and is identical to the position of these elements as illustrated in Fig. 7. The solid line position of the pull strip [2 and disc ill show their positions when a fixed element to be actuated, for example a contact I8, is positioned to engage an actuating element mounted at the center of the disc, for example a contact 20, when the pull strip 12 is under tension. It will be seen from this figure that when the fixed contact 18 is so positioned as to prevent the center of the disc from moving to the at-rest position indicated in dotted lines, the outer ends of the pull strip l2 extend downwardly from the central support. The position of the contact I8, with reference to the support, is an important factor in maintaining desired pressure between contacts l8 and 20 until the moment that the disc snaps into the other position.

The manner in which this optimum position of the fixed element or contact 18 is determined may be seen in Fig. 9, which is a cross-sectional view of the device taken at right angles to the views illustrated as electrical contacts.

cameos shown in'Figs. '7 and B. In this figure thesolid line position ofthe disc is the equivalent of the position shown in Fig. 1 with the pull strip [2 under reduced tension and the freeedges of the disc extending upwardly oneach side of the fixed element I8. When the parts of the pull strip 12 areplaced under tension the discsnaps to a reverse position with the free ends of the disc slanting downwardly and the disc carried element or contact 20 assuming an uppermost position. The ends of the disc in this action move through a distance indicated generally by the arrows a. It has been found that by placement of the fixed element l8 generally in the vicinity'of the center line b drawn between midpoints of the path of travel of thefree ends of the disc, that the optimum pressure conditions at engagementanddisengagement of the elements l8 and 20 areobtained, as well as an increase in the rapidity with which this engagement and disengagement is accomplished.

To illustrate the operation of the device, reference is made to Fig. wherein the elements or contacts I 8 and are shown in engagement, element I8 being at the optimum position described with reference to Fig. 9. The dotted line position of the disc I9 and of the pull strip l2 illus' trates the position of the disc and pull strip when the latter are under maximum tension and is identical to positions illustrated in solid lines in Fig. 8. When the tension in the pull strip decreases, whether due to expansion of the strip relative to the disc or to mechanical separation of the points of attachment of the strip to the support, the disc and pull strip move to the full line position shown in'Fig. 10, at which position pressure between the elements or contacts l8 and 20 is still maintained. As the tension in the strip continues to decrease, a point is reached when the power of the disc overcomes the tension in the strip and the device snaps from a position of firmcontact between elements [8 and 20 to the open position illustrated in Fig. 1. This action of the device inabruptly separating the ele ments I 8 and 20 is of particular importance in avoiding arcing when those elements are-electrical contacts. 1

The essential elements of the new snap action.

device and the operation thereof have so far been described without reference to any specific application, although the disc carried element and the actuated element of Figs. 7 to 10 have been These elements, however, are electrical contacts only when the device is incorporated in a circuit to be controlled thereby in response to expansion and contraction of the pull strip with increase and decrease of current therethrough. If the device is to be used, for example, as a thermostat, the disc and pull strip are of material having different thermal coefiicients of expansion so that snap action of the device results from differential expansion of the parts with change in ambient temperature. In such application of the invention the actuated element l8 may be any device adapted when actuated by engagement or disengagement to signify or control temperature conditions, the element 20 being suitably'shaped to cooperate with the actuated element. For

example, element 20 may be a button of insulating material and element l8 may be a spring arm carrying one of a pair of normally open contacts as in the arrangement illustrated in Fig. 18 hereinafter to be described.

In Fig. 11 the snap'action device of Figs. 1 to 6 is illustrated as a flasher for a load circuit, or as an overload protector, depending upon initial adjustment of the tension in the pull strip and upon the position of thefixed contact cooperating therewith. The device'is shown with the disc l0 thereof in the position corresponding to maximum tension in the pull strip I2, and with-a disc carried contact 29' in engagement with a flxed contact i8 positioned in the optimum position as described with reference to Fig. 9. The fixed contact I8 is connected through suitable supporting means 22 and wire 24 to I one terminal of a control switch 26. The other terminal of the switch is connected through a lamp or other suitable load 28 to one side of a battery 30, the'other side of the battery being-connected by means of alead 32 to the support 14 which in thisembodiment of the invention is of metal. When switch '26 is closed, current will flow from the battery through support 14, pull strip or wire l2, disk in, contact 20' carried thereby, contact l8, through switch 26 and load 28 to energize the load. With the pull strip under tension and the fixed contact positioned as above described, the device operates as a flasher. The load current is sufficient to heat the pull wire to thepoint where its expansion permits the disc to buckle and assume a position as shown in Figs. 1 to 3. This action separates contacts [8' and 20 to break the circuit, whereupon the pull wire cools. With the cooling and the attendant contraction, the disc will again buckle outwardly to close the contacts l8 and 28' and this alternate or flashing action will continue as long as the switch 26 is closed. If the device is'to operate as an overload protector the nut H is turned to reduce-the tension in the pull wires to such an extent that when the disc buckles into the contact open position due to excessive current through the-device, the disc will remain in that position and hold the circuit open, there being insufficient tension in the pull wire to return the disc to the contact closing position once the disc has snapped through equilibrium position. After the disc has snapped to open the circuit, the disc can be reset, that is, snapped to contact closing position, by outward pressure applied to the center of the disc, as by manual operation of a tool inserted through the axis of support [4 which in this instance would be formed with a suitable axial passage therethroug Figs. 12 to 14 show a specific embodiment of the snap action device in a switch structure. In these figures the disc is denoted by the numeral 34. It is creased or bent along a diameter in the manner described in connection with Fig. 1. The pull strip in this embodiment of the invention is formed of two parts, indicated as flat wires 36a and 36b, which are fastened to the outer periphery of the disc by welding or the like, with their inner ends similarly fastened to a transverse bracket member 38 providing the entire support for the pull strip and the disc. The pull wires are alined with the diametral crease or deformation of the disc 34 and are on the convex side thereof.

The sub-assembly of the operating portions of the switch, namely, the disc 34, pull wires 36a and 36b, nd bracket 38 are mounted within a thin recessed housing 40 of insulating material with the disc centrally disposed within a recess 42 and the ends 44 and 46 of the bracket 38' disposed within shallow recesses 48 and 50, respectively. The end 44 of the bracket 38 is firmly mounted within its recess 48 by a conductive rivet 52 extending through the housing and carrying one contact terminal 54 for the switch.

The other end 46 of the bracket 38 is adjustably held in its recess by a screw 56. Centrally of the recess 42 in which the disc is disposed is a fixed contact 58 fixed to the housing 40 and connected with a lug Ell to form the second terminal for the switch. The contact 58 cooperates with a disc carried contact 62 to open and close the circuit between terminals 54 and 60.

In order to adjust the tension on the pull wires 36a and 36b to obtain the desired operation, the bracket member 38 is slotted at 64 with an enlarged central part 66. The tension adjustments are illustrated in Figs. i l-A and i l-B. Fig. l i-A shows the means for increasing the tension on the pull wires, which comprises a pair of jaws B8 to deform the bracket member 38 to narrow the recess 84. To decrease the tension a cam member I is inserted in the enlarged section 88 of recess 64 as shown in Fig. 14-13 and rotated in position to widen the recess 66 the desired amount.

Adjustment of the spacing of contacts and 82 is accomplished by the adjustment of the screw 58 holding one end of the bracket member 38 in the housing 49. The bracket member is recessed at E2 and bent slightly as shown in Fig. 13 so that the screw 56 pulls the end 46 of the bracket into place. The resiliency of the metal bracket 38 is sufficient to retain the adjusted contact setting and the degree of adjustment is suincient to attain the optimum position or" the fixed contact relative to the movable contact on the disc.

By the simple addition of a bracket carrying a centrally disposed contact, the structure of Figs. 12 and 13 can be modified for operation as a two-way flasher. Such an arrangement is illustrated in Figs. 15 and 16 wherein elements corresponding to elements of the structure of Figs. 12 and 13 are identified with the same refer- I ence numerals. The additional bracket, which is indicated at 24 and carries a contact it on the underside thereof, overlies the bracket 33 and is disposed at right angles thereto with the contact :6 positioned within the opening 623 in bracket 38. in a recess '58 in the housing as by means of a rivet 89 which extends through the housing and serves as the electrical connection between the contact l6 and a terminal 82. The other end of bracket M which, like bracket 33, is sprung u wardly by bending at a weakened section adjacent the riveted end, is adjustably secured in a recess 8d of the housing by a screw ea. For cooperation with the contact "iii, a contact 88 is centrally mounted on the disc 34 on the convex side of the crease therein. When the above described structure is to be connected for operation as a two-way flasher, the spacing of contacts 58 and 62 is adjusted to the correct position for maintenance of contact pressure up to the instant that the disc snaps to separate these contacts and to close contacts 83 and iii. The load circuits to be alternately flashed are connected to terminals 69 and 82, and terminal 54 is connected through a suitable switch to the source of energy.

It will be understood, of course, that the current drawn by the load circuit connected to terminal 82 should be less than that drawn by the load circuit connected to terminal Ell so that there will be alternate expansion and contraction of the pull wires and hence alternate flashing of the circuits as the disc snaps back and forth from one contact closing position to the other.

If the structure of Figs. 15 and 16 is to be used,

One end of bracket '14 is mounted for'example as a load indicator, it is only necessary that contacts 62 and 58 be permanently electrically connected together, as by a light flexible conductor. Such an arrangement is illustrated in Fig. 1'? wherein the operating parts of the structure are shown connected for indicating by a pilot lamp the condition of a lamp load circuit. In Fig. 17 the flexible conductor electrically connecting contacts 62 and 53 is indicated at 99 and three lamps, 92, 9E. and 96 are shown connected in parallel between contact 58 and the negative terminal, indicated as ground, or a source of energy 98. A pilot lamp 100 is connected between the back contact 16 and ground and the bracket 38 supporting the disc and pull wires is connected through a switch [02 with the positive terminal of the source 93. With this arrangement the position of fixed contact 58 is relatively unimportant. It would ordinarily be moved out of engagement with contact 62. The operation of the above described circuit is as follows: When switch )2 is closed current flows through the pull wires, disc, connector and lamps e2, 94 and 95, assuming all lamps are in operating condition. The current through the pull wires under this assumed condition is sufiicient to cause the pull wires to expand and permit the disc to snap to the position to which it is constrained by the crease therein, in which position contacts 88 and 16 engage and pilot lamp Hi0 is lighted. Lamps 92, 94 and 98 will remain lighted because of connection 90 and the disc will remain in back contact closing position until and unless one or more of the lamps 92, 94 and 96 fail. Upon such failure, the reduced current passing through the pull wires causes sufificient contraction of the wires to snap the disc into the illustrated position with contacts 88 and 16 out of engagement. Pilot lamp 100 will thereby be extinguished, indicating failure of one or more of the lamps of a load circuit. The device may be made sensitive enough to respond to a relatively small change in load current so that failure of any one of a group of lamps can be promptly indicated by extinguishment of the pilot lamp.

In the arrangement diagrammatically illustrated in Fig. 17, should the pull wires, when expanded in normal back contact closing position of the disc, be short-circuited by the disc, they would cool and contract and cause the disc to snap into contact open position, thus extinguishing the pilot lamp and giving a false indication of lamp failure. Such false indication can be avoided by adjustment or contact 76 into a position to provide a stop preventing the disc from assuming its fully constrained position. Furthermore, as the disc itself is of resilient material and as the maximum tension is applied thereto at the points of attachment of the pull wires, the disc flexes slightly at these points in a direction tending to space the wires from the disc surface and hence to minimize the possibility of short-circuit of the wires by the disc. In applications where the pull strip does not carry current when the disc assumes the position to which it is constrained by the crease therein, shortcircuiting of the pull strip by the disc is often advantageous as it accelerates cooling of the strip and prevents burning out thereof should the device be inadvertently connected across an excessively high voltage.

In the particular applications heretofore described, the snap action of the device has been occasioned by expansion of the pull strip under '9 the influence; off heat, .eitheras aresult. of; the passage of current therethrough or as a result of'changein ambient temperature. In Figs. 18 and. 19, to whichreference may now be had, snap action of the device occurs as theresult of change ingtension applied mechanically to the pull wires. In-thisembodiment of the invention the disc is indicated by the, reference numeral I04 and the pull strip byvsections I 3a, I06b.- The outer ends of the pull strip parts are connected to opposite ends of the diameter of'the disc I04 as in previous embodiments. of the invention along the convex side ofthe-creasetherein. Theinnerends of the pull strips are. secured to azsupport member I00 having-a V -shapecl slot IIO therein forming; jaws I08a and I082): to which the strips are connected. The support member I08- iszof spring material and the jaws have a constraint therein tending to movethem apart. I A drum I'I-2 split into two semi-cylinrical sections and havingan axial slot I I4-thereinfor reception of the jaws: I080 and- W8?) carries a circumferential coil: II6 of expansible wire; which coil holds the halves. ofthe drum together and is under suiiicient. tension to force. the jaws Him and IMF) toward each other and thereby introduce tensionintothestrips I06a, I06b. To assure alinement ofthe. halves of the drum with-movement thereof toward and away; from-each other, a recess. H8 is formed in each drum half for. reception of a pin I20 carried by the other drum half. When the current is passedthrough the coil I:I6, as from leads I22, the expansion of the wire forming the turns of the coilzrelaxes the pressure between. the halves of the drum H2 4 andpermits theajaws I08a and I082) to move apart. sufiiciently 'to'reduce. the tension in the pull strip and permit the disc -I04-to snap into its normal constrained position. The snap action of the device resulting from the mechanical I change in tension in the pull strip may be employed for actuation of any external device. In the particular embodiment of the invention illustrated in Fig. 18'the device is arranged for open' ing and closing an external circuit in response to the current in the expansible coil H3. The device may therefore beconsidered as a relay. The external circuit isillustrated diagrammatically in Fig. 18 as comprising leads I24 and I26-connected, respectively, to an arm I28- carrying'a fixed contact I30 and a spring arm I32 carrying a contact I34, the tension inthespring arm. I32 tendingtoopenlthe contactsI30 and I34. An insulating button I36 carried centrally. by the disc I04 on the concave side-of the crease therein. engages spring, arm I32 when the. disc, is in the position corresponding to maximum tension in the. strip parts I06a, I06?) toforce the spring arm into-position to close contacts. I30 and I34. The above described arrangement is particularly adapted foruse when relatively small currents and high voltages in the controlling circuit are to be encountered. It will be appreciated that-but minor changesv in position of the jaws I08a and I081) are sufiicient to cause operation of the switch. It will also. be understood that whether the increase and decrease .in tension in the pull strip is occasioned by mechanical movementof the inner ends of the pull strip as in this embodiment of the invention, or as a. result of heating and cooling as in the earlier described application; a change inthe. distance between the points of, attachment. of the .pull strip .to thev disc occurs.v I

disc of. the snap.;-a,ction device of them- 10 vention may. have its inherent. constraint. intro.- duced in a variety of ways. Theconstraintmay resultfromthe formation in. the disc of a. diametral crease, as heretofore. described and such is the, preferred arrangement.v It is,not.nec.es.- sary, however, that the crease-occupy buta mini?- mum medialv portion. of the. disc as. a wider. but shallower; crease or troughcould. be, employed. For example, two creases equally. spaced n op.- posite sidesv of, a diameter couldbe provided, in which case the. section betweenthecreases. would be. relatively flat, or the. diametral, creaseor. channellcould be interrupted at, itscenter to provide a fiatportion uponv which a con-taster other op.- crating v element could be mountedg Also, the central crease or-channel. could terminateshorlt' of the periphery of, thedisc tdprovidefizit sun.- faces ior. attachmentof. the. endsof the pull. wire. In some instances it. might be. advisable pic: videstrengthening. ribs or ridgessymmetrically disposed. on opposite sides .of a. diameter. andb.e,-

, tween constraining. creases. for focusing. the

buckling forces toward the-center cfthedisc. Figs. 20. andZl twodifferent designsof discsuitable. foruse inthe snap action device of theinvention. in place. of. the singly creased disc. here.- tofore described are. illustrated. In Fig. 20is indicated a disc I38. having adiametralcrease I40. which terminates short of, the peripheryof the disc and isinterrupted at. the; center of the disc. This provides relatively bendable areas at the. centerof the disc; and at theperiphery'ad jacent the points of attachment of thepullmeans.

The. increased flexibility of the. disc atv thepoints of attachment; of-thepull-strip tendsrto prevent short-circuiting of, thes'trip by the-discwhenthe strip. is fully expanded as discussedwithreierence to the arrangement illustratedinFig. 17-... In F'ig. 21 a disc I42 is indicated which has crease lines I44v and. Ilia-symmetrically disposed. on opposite sides of thediameter. D of, the discrparallel to the. pull strips. (not. shown). Intermediate the crease lines I44 and I46 arestiiiening depress sions I48 and I50fwhich extendradially, and'symmetrically withrespect. to thediameter of the disc. These depressions. I43 and I50 terminate short of the. center of thedisc. and short of. the periphery and. serve, as reinforcement. of the central section between the creaselines I44 and. I46. It; willfbe understood that. the view of the disc I42. showninEig... 21 is that taken .from. the. concave side of the creaselines. The. discI42 isalso providedwith short upraisediridges. I52. extend.- ing. from the. periphery valong/the. diameter dis,- posed at. from; the diameterDh These ridges I52 assist, when the-disc is snapped, in localize ing theposition. of theopposite, fold in the disc. The disc I42 with its crease lines, depressions. and ribs may conveniently be formed by stamping from a die. Conveniently shortand; narrowldepressions I54 at oppositeendsof the diameter. D may be simultaneously formed for; providing points of attachmentfor the: ends of a pull strip which, as will be understood, willbe. securedto the disc-along the underside of thedisc asviewed in Fig. .21. The. depressions, I54 also serve to space the pull strip fromthedisc and'thereby tiend to prevent, shor-t-circuiting .thereotby the The snap action device of the inventioncomprising essentially the diametrically constrained disc, the laterally flexible pull strip OhWiIiCg, and the central support to which the pull strip is Se;- curedand bywhich itis tensioned, has now been described, The snap action of the 'deviceroccurs as a result of change in tension in the pull strip. When'the device is thermally actuated, whether by passage of current therethrough or by changes in ambient temperature, the tension change in the pull strip is caused by expansion or by contraction of either the pull strip or of the disc, depending upon the particular materials employed and their relative dimensions. When the disc is mechanically actuated the change in tension in the pull strip occurs as a result of change in overall length of the pull strip and hence to avoid response to ambient temperature the disc and pull strip in this case should be preferably of material having similar thermal coefficients of expansion. Thus' 'the dimensions of disc and pull wire together with the specific materials of which they are formed depend upon the particular use to which the device is to be put. For a switch, for example, a nickel alloy containing at least 90% nickel, is recommended for use both for the disc and for the pull Wire. The disc may have a diameter of A and a thickness of .005 and the pu l strip may be Tg wide and .003" thick. A switch of such dimensions and of such material is suitable for use, for example, as a flasher for automobile direction signal and stop lights. A snap action device of the same order of dimensions but with the disc of Invar (nickel steel containing 36% nickel) and the pull strip of nickel or with the disc of nickel and the pull strip of Invar is suitable for use as a thermostat. Larger and smaller discs and pull wires may of course be employed.

This application is a continuation in part of abandoned U. S. applications Serial No. 543,623. filed July 6, 1944 for Thermal Control Means and Serial No. 173,411, filed July 18, 1950 for 'Thermal Device for Circuit Control.

I claim:

1. A snap action device comprising a disc of resilient material having an inherent diametral deformation therein, laterally flexible pull means secured to the disc at opposite ends of the deformation therein and extending along the convex side thereof, and means disposed adjacent the center of the disc and secured to said pull means for supporting the device and tensioning the pull means, said disc being wholly supported by said pull means.

2. The combination with the snap action device according to claim 1, of a separately supported element positioned on the axis of the disc and on the concave side of the deformation therein for engagement by the disc when the disc is buckled under the tension of the pull means into a position wherein it is curved concavely toward the central support about a diameter 90 to the diametral deformation.

3. The combination according to claim 2 wherein said element is positioned to limit the movement of the center of the disc during buckling thereof.

4. The combination according to claim 3 including an element centrally mounted on said disc on the concave side of the deformation therein for actuating said first mentioned element by engagement therewith.

5. The combination according to claim 4 wherein said elements are electrical contacts, said disc is of metal and said pull means is of expansincluding means associated with said central support means for varying the tension in said pull means.

7. The snap action device according to claim 1 wherein said pull means comprises two flexible strips each connected at one end to the disc, the other ends of said strip being connected to different points on said support means, and means for varying the spacing between the points of connection of the strip to the support means to vary the tension in the pull strips. 7

8. The snap action device according to claim 1 wherein the disc and pull means are of material having the same coefficient of thermal expansion whereby the tension in the pull strip is independent of the ambient temperature.

9. The snap action device according to claim wherein the disc and pull means are of material having different coefiicients of thermal'expansion whereby the tension in the pull strip varies with the ambient temperature.

10. A snap action device comprising a disc having an inherent diametral deformation therein tending to cause it to assume a constrained shape, a support element having laterally flexible pull means fastened thereto and radiating out therefrom, the outer ends of said pull means being fastened to points of said disc at opposite ends of the deformation therein and on the convex side thereof whereby when the tension in said pull means is reduced the center of the disc snaps in one-direction to assume its constrained shape and when the tension in said pull means increases the snap action of the center of the disc occurs in the other direction.

11. A snap action device according to claim 10 including means associated with said support means for operating upon the central portion of the pull means to vary the tension thereof to snap the disc from one position to another.

12. The snap action device accordingto claim 10 wherein said pull means and disc are of electrical conducting material and the tension in said pull means is varied by differential expansion and contraction of said pull means and disc with passage of current therethrough.

13. The snap action device according to claim 10 wherein said pull means and disc are of material having different coefficients of thermal expansion and the tension in the pull means is varied by diiferential expansion and contraction of the pull means and disc with changes in ambient temperature.

14. The combination with the snap action de vice according to claim 10, of a separately supported element positioned on the axis of the disc and on the convex side of the deformation therein for engagement by the disc when the center of the disc snaps in the direction to assume its constrained shape as a result of reduction in tension in the pull means.

15. A snap action device comprising a controlling metallic disc-like member having an initial constraint incorporated therein tending to cause it to assume the constrained shape, a support element having pull wire means fastened to the end thereof and radiating out therefrom, the outer ends of said pull wire means being fastened to spaced points of said disc, said points being on the opposite sides of the center of the disc and so arranged with respect to the disc that when the pull wire means expand the center of the disc moves with a snap action in one direction and when the pull wire means contract a snap action of the disc center occurs in the other direction.

16. The device according to claim 15 wherein said pull wires are of material having a coefficient of thermal expansion diifering substantially from the coeflicient of thermal expansion of the metallic disc-like member whereby differential expansion and contraction of said disc and pull Wires under changes in the ambient temperature causes snap action of the disc center and wherein said support means are adjustable for varying the tension in said pull wires.

17. A thermal switch device comprising a sup port, a buckling member having a portion adapted to occupy two different positions for operating a circuit opening and closing contact, and linear expansion pull means carried by said support and fastened at two spaced points to said buckling member to control the buckling thereof to cause said portion to occupy one of said positions responsively to current flowing through the expansible means, and said buckling member being carried by said expansible pull means, the buckling member being in the form of a constrained disc with the outer ends of the expansible means fastened to one side of the disc at diametrically pposite points adjacent its periphery.

18. A thermal switch device comprising a support, a buckling member having a portion adapted to occupy two different positions for operating a circuit opening and closing contact, and linear expansible pull means carried by said support and fastened at two spaced points to said buckling member to control the buckling thereof to cause said portion to occupy one of said positions responsively to current flowing through the expansible means, and said buckling member being carried by said expansible pull means, the buckling member being a disc of comparatively thin spring metal doubly constrained by having a transverse bend formed therein and by the pull of the expansible means fastened at its ends to the convex side of said bend.

19. A thermal switch device comprising a sup" port, a buckling member operating a circuit opening and closing contact and linear expansible pull means carried by said support and fastened I at two spaced points to said buckling member to control the buckling thereof responsively to current flowing through the expansible means and said buckling member being carried by said expansible pull means and the latter comprising two parts disposed in line with each other and said support comprising two relatively adjustable portions to which are fastened respectively the inner ends of the expansible pull parts.

20. A circuit controller comprising a disc having a diametrical crease and carrying a contact at the center of the concave side, a pair of expansible and contractible Wires having outer ends fastened at opposite points on the periphery of the disc, a supporting means disposed at the center of the convex side of the disc with the other ends of said wires being secured thereto to wholly sup port the disc and a fixedly mounted contact positioned in operable relationship with the first said contact.

21. A snap action device comprising a diametrically creased disc, an element centrally mounted on the concave side of the disc, a pair of radially disposed expansible and contractible strips on the convex side of the disc in alinement with the diametrical crease and fastened at their outer ends to the periphery of the disc, centrally disposed supporting means positioned on the convex side of the disc with the inner ends of the strips secured thereto to wholly support the disc, and a fixed element mounted in cooperating relationship with the disc carried element.

22. A snap action switch comprising a disclike plate of resilient material creased along a central line to displace the portions of the plate on each side of the line to form an included angle of less than 180, a contact mounted on the center of the concave side of the plate, a pair of radially disposed pull wires on the convex side of the plate in alinement with said line and fastened at their outer ends to the edges of the plate, and centrally slotted supporting means on the convex side of the plate with the inner ends of the pull wires fastened thereto on each side of the slot, the width of the slot being adjustable to control the tension on the pull Wires.

23. A thermal switch device comprising a support, a substantialy circular buckling member carrying a contact and having an inherent constraint tending to move said contact through a dead center position to occupy a circuit controlling position and linear expansible pull means carried by said support and fastened to said buckling member at two spaced points on the opposite sides of a transverse line passing through said contact to control the buckling thereof responsively to current flowing through the exp-ansible means and said buckling member being carried by said expansible pull means.

24. In a thermal switch device of the character set forth in claim 23 wherein the support comprises two adjustable parts and said linear expansible pull means comprises two parts fastened spectively to the adjustable support parts.

JOSEPH SCHMIDINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

